It was the cardinal sin, if not in team sports than in basketball, if not in basketball than certainly for the Ubuntu Boston Celtics—playing for oneself rather than one’s team, playing for a contract rather than wins. And in a twisted irony that was heart-wrenching, frustrating and sad, Glen Davis did not just hurt his team, but also himself and his contract situation.

“To me, I thought it was more in between his ears than his play,” Doc Rivers told WEEI. “I thought the whole contract thing affected his play. I thought he had the wrong focus at times because of that. I think when you stray away from just being a team player and being the role that you’re given, I think you struggle. I think all players do. And I thought Baby did that.”

Reading Rivers’ comments, one senses Davis may have played his final game in Boston. Rivers felt Davis gained weight by the end of the season. He felt Davis was playing selfishly. He and Davis have always bumped heads; hell, Davis even began this season—on the very first day of training camp—by calling Doc out, saying he never understood his role. But these comments by Doc were different. This wasn’t just a half-joking barb about Davis’s weight; it was a public attack at what he deemed an insufficient attitude.

“I thought scoring was way too important to him, instead of being who he is,” Rivers continued. “Baby’s never going to be a great scorer in our league, but he can score. What Baby has to be is an energy player, a guy who takes charges. When you look at his charge numbers from the first 40 games and then the last 40, they’re cut down, he got very few of them. I thought a lot of that had to do with he became in thought offensively instead of being an energy player.”

Two seasons ago, after a 2008-’09 campaign that saw Davis fill in admirably for Kevin Garnett, he thought he had earned a larger contract. He entered the summer as a restricted free agent and figured teams would throw money at him—after all, he had averaged 15 points and 6 rebounds during the playoffs. He had hit a game-winner against Orlando. Yeah, he had accidentally run over a kid afterward, but wasn’t that just part of his fun-loving appeal? He was young, his game had improved swiftly and emphatically, and the money was sure to come flying his way in bunches. But being a restricted free agent doesn’t always work out well.

Danny Ainge and the Celtics bided their time, playing things cool, letting other teams establish Davis’s market. Except no other teams offered him a contract. Anderson Varejao earned $42.5 million. Charlie Villanueva, $35 million. Chris Anderson, $26 million. Brandon Bass, $18 million. But, whether it was because the Celtics were expected to match any offer or because undersized power forwards are a dime a dozen, not a single team offered Davis a contract. He was left to sign with the Celtics—two years, $5 million,with incentives to make the deal as much as $6 million if he kept his weight down. Or, in other words, nowhere near the type of money Davis thought he had earned.

Since then, one got the feeling Davis was always upset with his role. Not just because he wasn’t sure what that role was, but because he had proven he could start in this league yet had no chance to start in Boston—not as long as Kevin Garnett still wore Green. Davis considered himself a starter, wanted to start, would have given anything to start. But fate and the limitations of restricted free agency left him earning less money than he expected, playing fewer minutes than he had hoped, taking a step back in what he thought was going to be another breakout year. Still, he and Nate Robinson won Game 4 of the NBA Finals almost by themselves. Davis’s energy was crucial to Boston’s second unit. He became Shrek overnight, a press conference sensation, and he was already a fan favorite, a key element to Boston’s title chances even if his role wasn’t exactly what he wanted. If only he had seen things that way.

This past season still started out so well, but somewhere in midseason—and the slide began earlier than most observers thought—the weight of expectations and the pressure of playing in another contract season cracked Glen Davis. He began taking long jumpers early in the shot clock. He stopped rebounding. His charges taken, as Rivers noted, dropped severely. Twice, Davis lost track of who he was (not to mention his mind) and fired three-pointers at pivotal moments of games—one of the errant long bombs was against Memphis and lost Boston the game, on a final play designed for Paul Pierce or Ray Allen. The hero complex had gotten the best of Davis. A player who had succeeded because of his energy and willingness to contribute the little things suddenly thought he was above all that. He played with the trigger-happy right hand of a star, often taking more shots than any of his better and more accomplished teammates.

“He can help us or any other team,” Rivers said. “But, to me, only if he plays the right way.”

He didn’t always play the right way, didn’t always make the right play. Still, after a season that saw him drive down his value, after being sent home far too early for vacation, Davis wanted to talk about a starting role.

“I know I can (be a starter). It’s not a think or a feel. I know I can,” Davis told MassLive. “I want to be a player in this league. I feel like I’ve got a lot more to offer. I want to show the world my talents, whether it’s here in Boston, or wherever.”

What went left unsaid was that he desperately tried showing the world his talents this year in Boston. Instead, he just exposed himself and minimized his next contract. Nonetheless, the comment summarized Davis’s entire second half of the season. He was no longer happy playing for a contender, not if that meant he came off the bench. He could have been invaluable as a sixth man—hell, for a while, he was—but in his mind, at least, Davis had outgrown that role (no pun intended).

He doesn’t want to come off the bench anymore and he wants to make more money; neither of those things are likely to happen in Boston.

Sometimes, it’s mutually beneficial to part ways.